The demands on automobiles for better fuel economy have been increasing in recent years as concern with environmental issues has been rising. Hence, better fuel economy is also required of rubber compositions used for automotive tires. For example, rubber compositions containing a conjugated diene polymer (e.g. polybutadiene, butadiene-styrene copolymer) and filler (e.g. carbon black, silica) are used as the rubber compositions for automotive tires.
Patent Literature 1, for example, proposes a method for improving fuel economy. The method uses a diene rubber that has been modified by an organosilicon compound containing an amino group and an alkoxy group. In recent years, however, further improvement in fuel economy has been demanded. Moreover, since some other properties required of the rubber compositions for automotive tires, such as wet-grip performance and abrasion resistance, generally have trade-off relationships with fuel economy, it has been difficult to achieve these properties at high levels in good balance.